The present invention relates to locknuts, and more particularly to locknuts including a spring coil or band.
All-metal prevailing torque locknuts are often specified for use in extreme temperature and/or high vibration applications. One of the more common types of locknuts has distorted threads to provide an interference fit with the mating male thread. A description of this type of locknut may be found at http://www.fastenermart.com/html/all-metal-lock-nuts.html. Locknuts with distorted threads have a very high prevailing torque which, in some cases, may be as high as the design torque of the bolted joint itself. This high prevailing torque makes installation of the locknut slow and difficult and control of joint clamp-up problematic. Further, if the joint consists of a number of all-metal locknuts, it is difficult to maintain uniform or desired clamp-up at all of the bolt locations. This can lead to structural weakness and to leaks in applications where fluid seals require uniform clamp-up to maintain proper gasket or joint compression.
Another common type of locknut is a split beam or flexloc locknut. A description of this type of locknut may be found at http://www.fastenermart.com/html/flexloc-nuts.html. This type of locknut has a nut body that includes a top portion with six narrow slots spaced 60° apart, thereby forming six flexing beams. These beams are bent inward slightly to provide a grip on the male threaded member. This type of locknut is relatively expensive compared to the distorted thread style locknut.
Both types of prevailing torque locknuts are only able to be used for a few on-off cycles. In the case of un-plated stainless steel locknuts, just one use is recommended. Consequently, the ability to reuse these locknuts is quite limited.